Update Mixpanel SDK import instructions

Clarified the import statement for Mixpanel SDK in the documentation.

Author: harryyiump

pages/docs/quickstart/install-mixpanel.mdx

@@ -52,7 +52,7 @@ Replace `YOUR_TOKEN` with your project token. You can find your token [here](htt
 You can learn more about configuring Session Replay and Heatmaps [here](/docs/tracking-methods/sdks/javascript/javascript-replay).
 
 ```js Javascript
-//Import Mixpanel SDK
+//Import Mixpanel SDK (only required for npm and yarn)
 import mixpanel from "mixpanel-browser";
 
 // Near entry of your product, init Mixpanel